Amy Love Tomasso

Across Massachusetts, rising rents, scarce inventory and shrinking household size are intensifying housing unaffordability. To counter these market and demographic pressures, the state needs to build more housing of all types, sizes, scales and price points.

An underexplored opportunity to increase housing diversity lies in what was once common in our towns and cities: human-scaled multifamily housing that fits between single-family homes and mid-rise apartment buildings.

Known as “missing middle” housing, these home types – including  duplexes, triplexes, townhomes and cottage clusters – are ideal for walkable neighborhoods, shorter commutes and a broader range of household needs and preferences.

Yet today, even in places where multifamily zoning has expanded, the missing middle remains largely absent. Local rules around lot size, setbacks, parking and building codes make it financially unfeasible or practically unworkable to produce smaller-scale multifamily homes at a meaningful scale.

As I proposed in a series of working papers published through the Harvard Joint Center for Housing Studies this year, a missing middle policy agenda for Massachusetts should certainly include, but not stop, at legalizing missing middle housing in name alone.

While allowing home types like duplexes and triplexes by-right and increasing residential density are important steps, unlocking housing supply will also require serious reforms in building code, development oversight and dimensional regulation.

Consider three concrete reforms that add more nuance to the missing middle policy conversation, and are ultimately consequential for bringing back missing middle housing at scale.

Loosen Dimensional Rules

First: Loosen rules on lot coverage and setbacks, and allow moderate height increases.

Many towns’ zoning codes require large lot sizes, deep setbacks, and relatively small building coverage, even where infrastructure exists.

Raising allowable lot coverage to between 30 percent and 60 percent and reducing or eliminating setback requirements could enable small multifamily housing on many infill and under-utilized lots.

For communities with transit or services nearby, allowing 3- or even 4-story construction, especially in larger municipalities, could dramatically increase yield.

Streamline Development Review

Second: Streamline the development review and permitting process for small multifamily projects.

Today, missing middle proposals often face the same lengthy, discretionary processes as large-scale developments. That uncertainty, coupled with high fees and costs, discourages many would-be builders.

Workable alternatives include allowing by-right construction for small multifamily homes, creating pre-approved house plans, reducing fees proportionally per project size, and speeding up review timelines. Online or automated permitting tools can result in added time savings.

Single-Stair Reform, and More

Third: Reform building codes for small multifamily housing, especially for structures up to six units.

Under current Massachusetts code, buildings of three units and above trigger more onerous requirements like sprinklers, multiple stairwells and fire walls, often making them cost-prohibitive.

A “code carveout” for six-unit or fewer structures – including allowing simpler single-stair egresses and more flexible design standards – could open up many more parcels in urban, walkable neighborhoods.

All those infill lots add up when it comes to building new homes.   

Let’s Enable Gentle Abundance

Land use reforms that propose increased housing abundance can face commonly-touted anti-growth sentiments. Critics and NIMBYs fear increased density will inevitably result in loss of neighborhood character, more traffic or overburdened infrastructure.

But the history of Massachusetts’ cities and towns tells us otherwise. Before the imposition of restrictive mid-century zoning, triple-deckers, rowhouses and modest multifamily buildings were common, and provided attainable housing for working families, multigenerational households and new Americans.

Collectively, these reforms would create the kind of gentle density that preserves neighborhood scale while producing the housing variety that shrinking households, downsizing older residents or aspiring first-time homebuyers desperately need.

Importantly, many of these reforms don’t require massive public spending; instead, they rely on smarter regulations, from building code carveouts to streamlined permitting and more permissive lot/dimensional rules, to unlock existing land and infrastructure opportunities.

That’s why state policymakers should treat missing middle reforms as the next wave in housing policy, not a legislative compromise or afterthought. If done right, Massachusetts can restore the housing abundance, local character and ingenuity that the iconic triple-decker – the state’s time-honored missing middle housing type – first brought to the commonwealth.

Amy Love Tomasso is the director of policy innovation at Ivory Innovations, and a former research fellow at the Harvard University Joint Center for Housing Studies.